MOLECULAR-CLONING, EXPRESSION ANALYSIS, AND CHROMOSOMAL LOCALIZATION OF MOUSE HMG1-CONTAINING SEQUENCES

We isolated clones encoding the mouse high-mobility-group (Hmg) chroma tin protein, Hmg1, from a 7.5-day mouse embryo cDNA library. The trans lated amino acid sequence encodes a protein of 24,890 daltons and is i dentical to previously characterized mouse, rat, and hamster Hmg1. How ever, comparison of the two mouse Hmg1 cDNA sequences revealed nine se quence alterations. This observation, together with the finding of a c omplex pattern of hybridizing bands in genomic Southern analysis, sugg ests that mouse Hmg1 is encoded by a multigene family. The expression of Hmg1 was examined by Northern analysis of RNA isolated from the ear ly mouse embryo and revealed a predominant 1.5-kb transcript in conjun ction with low levels of a 2.5-kb transcript. Further analysis of mous e embryos by in situ hybridization showed that Hmg1 transcripts are ex pressed in high abundance during early mouse embryogenesis. As develop ment progresses, Hmg1 transcript abundance is modulated in a spatially restricted and developmentally regulated manner. Chromosomal localiza tion with recombinano inbred strains revealed that Hmg1-related sequen ces are widely dispersed in the mouse genome. Here we also report: the mapping of six Hmg1 loci to mouse Chromosomes (Chrs) 10, 13, 16, and 17.